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Custom functions will run in both FileMaker Pro and FileMaker Pro Advanced. Newly defined functions appear under their own category in the functions list of the Specify Calculation and Edit Custom Function dialog boxes. If you do not wish to reveal your custom functions, you can disable their display in these dialog boxes.
-- sent from my iPhone4 --
Custom Functions will run in any of the Clients FileMaker Pro, FileMaker Go, FileMaker Runtime. You only need FileMaker Advanced to "Edit" or "Create" them.